I have a use case where I want to pre-process/post-process data fetched from S3 using Tableau's Amazon Athena Connector before/after loading it into Tableau. Is there a way to do this? Such as creating a wrapper around Tableau's Amazon Athena Connector?

For using Tableau Desktop to do some data processing you can join and blend data tables together for use. Also using the initial SQL or the custom SQL capabilities when connecting to Amazon Athena will allow you to do some additional processing.